This invention relates to ink-jet print cartridges, and particularly to handling of residual ink that is present from time to time on the exterior of the cartridge.
An ink-jet printer includes one or more print cartridges that contain liquid ink in a reservoir. The reservoir is connected to a print head that is mounted to the body of the cartridge. The print head has tiny orifices that enable ejection of minute droplets of ink from the print head to a print medium, such as paper, that is advanced through the printer.
Many ink-jet printers include carriages for holding the print cartridge(s). The carriages translate across the width of the paper as the cartridge ejects ink droplets to the paper. Each time the carriage crosses the paper, a swath or effective print zone can be covered with ink as needed to print an image or text. Between carriage translations, the paper is advanced so that the next swath of the image may be printed.
Oftentimes, especially for color images, the carriage is translated more than once across the same print zone. With each such translation, a different combination of colors or droplet arrangements may be printed until the complete image is formed. Thus, a carriage and the cartridge it carries often move very close to wet or partially dry ink that was applied during an earlier translation.
The ink droplets are expelled through orifices that are formed in an orifice plate that covers most of the print head. Not all of the expelled ink is deposited upon the print medium, however. A small quantity of ink remains on the print head in puddles in the area near the orifices. This residual or waste ink needs to be removed so that it does not collect to an extent that it would interfere with the trajectory of subsequent droplets that are expelled through the orifices. Such interference will degrade the quality of the printed image because subsequent droplets will not be placed on the print medium as intended.
Even if residual ink does not interfere with the trajectory of subsequently expelled ink droplets, its presence may create other problems. For instance, partially dry ink on the cartridge body becomes tacky or sticky. In some printing environments, the tacky ink may collect small paper fibers or similar contaminants present in the printer. Even before the residual ink becomes tacky, its surface tension will retain particles such as these fibers. Furthermore, partially dry ink can clog the orifices on the print head, which will cause poor print quality.
Fibers that stick to the tacky ink can extend therefrom into contact with the print media. In instances where these extending fibers contact ink on the paper (as is most likely to occur during the multi-scan print mode mentioned above) the carriage movement drags the fiber across the wet ink and produces undesirable streaking of the ink.
Irrespective of whether ink streaking occurs, it is desirable to prevent the spread of residual ink to cartridge or printer components that may, over time, be degraded by the corrosive nature of certain ink formulations.
Current versions of ink-jet printers often include mechanisms for periodic servicing of the cartridges. These mechanisms are often referred to as service stations. The carriage occasionally moves away from the print media and into engagement with the service station. One of the functions of the service station is to wipe away the residual ink from the orifice plate of the cartridge, to avoid print quality problems, such as orifice clogging.
In the past, the residual ink that is wiped from the orifice plate has been deposited in storage trenches formed in the smooth plastic body of the print cartridge near the orifice plate. Even if the ink is properly deposited in the trench, it is stored there in a pool that becomes tacky and susceptible to collecting fibers that cause the ink streaking problem mentioned above.
Sometimes, the service station wiper does not properly engage the print cartridge to deposit the residual ink in the trench. Also, the portion of the cartridge that is wiped, including the trench, is usually very close to parts of the carriage (datum features) that secure the cartridge in a precise position relative to the carriage for accurate printing. As a result, some of the ink is inadvertently transferred from the improperly engaged wiper to these carriage parts (or to other parts of the cartridge). The residual ink on these carriage parts builds up over time. Although such buildup is gradual, the residue on the carriage is not removed with each cartridge replacement so, eventually, it can accumulate to an amount sufficient to cause problems, such as ink streaking. Additionally, the residual ink on the carriage may spread to and interfere with other printer components that may contact the carriage.
The present invention is directed to handling residual ink in a way that avoids the above noted problems. In one preferred embodiment of the invention, an ink-jet print cartridge is equipped with an ink-receptive member such as an absorbent pad. The pad is located so that a service station wiper will move the residual ink from the orifice plate and to the pad.
The pad absorbs the ink. In essence, the ink is sequestered on the cartridge, in the pad. Preferably, the pad is quite porous so that the ink is drawn into the absorbent pad so that the volatile components of the ink quickly evaporate to reduce the likelihood of developing a tacky area over the pad.
Moreover, the porosity of the pad means that, as compared to a solid surface, the exposed exterior surface of the pad is greatly reduced, thereby reducing the amount of ink that can be carried on that surface. As a result, the exterior surface of the pad will have a correspondingly reduced tacky area to which fibers may stick. Even if a tacky area does develop, the reduced area of the exposed surface (hence, the reduced amount of ink for holding fibers) means that any fibers that are temporarily held by the tacky area of the pad will more readily wiped away, or be free to fall off (and not cause ink streaking) as soon as the area dries.
The ink-receptive material may be mounted to the cartridge body in any of a number of ways. In one preferred embodiment, the material is located so that a service station wiper will immediately engage the material after wiping the orifice plate. Thus, the residual ink is moved onto the ink-receptive material (and off the wiper) before the wiper moves into contact with a carriage part.
In another preferred embodiment, the cartridge body is shaped to provide a scraper for scraping the residual ink from the passing wiper. The scraper is configured and located so that the ink scraped from the wiper is deposited on the absorbent pad.
Other advantages and features of the present invention will become clear upon study of the following portion of this specification and the drawings.